1. Field of the Invention
This invention pertains to a turbo machine having a driven rotor shaft extending at least on one side through the machine housing wherein the rotor shaft is provided with an axial seal arrangement with at least one dry gas seal which is impinged or charged with barrier gas and whose leakage is eliminated via a leakage conduit.
2. Background and Material Information
Machines of this type are known, for example from German DE 39 25 403 and serve for example, as turbo compressors or gas turbines. In this type of machine the rotor of the turbo machine is retained in a closed housing whose inner area is under high gas pressure.
The passage of the rotor shaft, through the housing to the outside or to an intermediate chamber is sealed via a seal arrangement in order to prohibit the exiting of the gas under pressure from the inner area. As a rule, when both sides of the rotor, carried on the shaft, extend through the housing such a seal arrangement is provided on both sides thereof, or in the case of a single sided axial opening, with machines of the overhang type, such a seal arrangement is utilized only on this single opening.
Dry gas seals, that are impinged or charged with a barrier gas have proven themselves to be particularly low in friction and low in losses, wherein the sliding surface of a sliding ring is pressed against a corresponding sealing surface, while maintaining a minimum clearance so as to minimize the exit of the pressure gas from the inner area whereby the leakage of the seal is kept at an as small as possible value and at the same time a clearance is produced so as to permit non-contact running or operation of the seal. The small, though still remaining leakage is, as a rule, channeled or removed to the outside. At low pressures, as a rule a single dry gas seal is sufficient. At higher pressures however and in order to obtain increased safety, the primary inner dry gas seal is followed by a secondary outer dry gas seal of analogous construction which seals the inner leakage area against the outside. This outer dry gas seal preferably is only called into action and is effective only when the primary leakage is excessive, particularly if there is a defect in the primary inner dry gas seal. If necessary more than two dry gas seals can be arranged in tandem.
In turbo machines which process dangerous gases, particularly explosive or toxic gases, it is especially important and urgent that the exit or leakage of these dangerous gases, under pressure, is prevented from the inner housing areas or to reduce same to a minimal value in order to avoid a catastrophe. In order to achieve same, on dangerous areas of the machine, for example in the proximity of the gas ducts, suitable gas sensors are provided which preferably have specific detection sensitivities for the gas to be detected and which, upon exceeding a specific gas concentration, emanate a warning or alarm signal or initiate suitable countermeasures. This however requires additional complicated devices which in addition can react initially only when already sufficient amounts of gas have exited from the housing in order to initiate the release of a signal. The required time delay however is often insufficient in order to totally prevent a catastrophe.